Field of the Invention
The present invention relates to an electrical actuator system for adjustable furniture, preferably height-adjustable tables. The invention also relates to a control box and an adjustable piece of furniture.
The Prior Art
The explaining of the invention takes as its point of departure height-adjustable tables having a tabletop mounted on a subframe. The subframe comprises a supporting frame for the tabletop and linear actuators designed as lifting columns having the appearance of a table leg which, at the lower end, is provided with a foot. The supporting frame is mounted at the upper end of the linear actuators. More specifically, reference is made to the type of table shown in FIG. 3 in EP 2 160 958 to Linak A/S. The linear actuators comprise a rectangular, box-shaped motor housing on an upper end of telescopically arranged profiles. The motor housing serves as a mounting plate for the linear actuators, in that there are mounting holes for screws in the two parallel side walls and in one end wall. The supporting frame comprises two parallel longitudinal members and one transverse member towards the end thereof. The distance between the longitudinal members is matched to the width of the motor housing in such a way that the motor housing fits between the longitudinal members. The linear actuators are secured with screws between holes in the longitudinal members intended for this purpose, just as the motor housing can, with one end, be secured to the transverse member with screws. The height of the longitudinal and transverse members are matched to the height of the motor housing on the linear actuators, so that the motor housing sits concealed and protected between the side members.
For logistical and shipping purposes, the tables are presented unassembled, so that they take up as little room as possible and can be shipped as a flat package. The tables are typically first assembled on the premises of the end user, where the feet are mounted on the linear actuators, the supporting frame on the top thereof, and then the tabletop. Wiring for the linear actuators, control box and operating panel is mounted last and positioned wherever seems appropriate in the particular case. The control box thereby comes to take up an arbitrary position beneath the tabletop, and the cable guiding follows this. The cables are guided unprotected and in an arbitrary manner beneath the tabletop, and surplus lengths of cable are simply rolled up and more or less temporarily clipped up and suspended beneath the table top. Inappropriately, the cables are positioned loose in the cable tray. To keep the cable guiding under control and avoid unsightly cabling, a cable tray may be mounted under the table. Since the cable tray contributes to the table's appearance, it must be designed so that it blends in with the design of the table. However, in a market in which the price of tables is under pressure, this is an unacceptably expensive solution.
As to height-adjustable desks or work tables, it is desirable to position lifting columns, control box and operating unit in such a way that the user is provided with as much free space beneath the tabletop as possible. From a design point of view it is also desirable for particularly the motor housing and control box of the lifting columns to be virtually invisible. This similarly applies to the cabling between the control box and lifting columns and operating panel respectively. To satisfy this requirement, the idea was also conceived of mounting the control box and various cables within the dimensions given by the two longitudinal members of the supporting frame on which the tabletop is mounted. The distance between the two longitudinal members is, as already mentioned, given by the width of the motor housing. In order to be able to fit the control box it is therefore necessary to reduce the outer dimensions thereof. Since the power supply to the control box typically is based on a ring-core transformer, the need to reduce the dimensions of the control box presents a spatial challenge. The reason for this is that the dimensions of the ring-core transformer cannot be altered directly. Moreover, with a view to the operational stability and useful life of the control box, it is desirable to retain the ring-core transformer. This is because, in some situations, the actuators can draw in the region of 15 amperes, which a ring-core transformer is able to produce. While the dimensions of ring-core transformers have been successfully reduced slightly by optimisation of said transformers, the ring-core transformer must still be positioned abutting the inner surfaces of the control-box cabinet. Thereby the width of the control box can be reduced so that it can be fitted between the two longitudinal pieces with perfect accuracy.
To simplify the cable connection to the control box and minimize the risk of faulty connection, it is furthermore appropriate for the mains voltage connector of the control box to be kept separate from the low-voltage connector to the lifting columns, and the modular connector to the operating panel. It is therefore appropriate for the mains voltage connector and the low-voltages connectors to be placed on opposite ends of the control box. In respect of the given installation measurements, this positioning of the connectors of the control-box results in the cable between at least one of the lifting columns and the control box not being guidable within the aforementioned installation measurements. Although this cable can be guided outside the dimensions given by the longitudinal members, this is not an appropriate solution.
In EP 2 452 589 A1 to Linak A/S a solution is disclosed wherein two longitudinal cable guides in the form of grooves are formed on the rear side of the control box, by which means one has—within the dimensions given by the longitudinal members—the possibility of guiding cables from the end of the control box, in the cable guides beneath said control box and to the linear actuator at the opposite side of the table. By this means, the user achieves the desired free space under the table and the height-adjustable table further has the desired design-consistent appearance. However, the cables must have been located in the cable guides before the control box could be mounted on the underside of the tabletop.
The invention relates to the problem of an adjustable table, in that a linear actuator may be connected to the control box without exceeding the installation measurements given by the longitudinal members beneath the tabletop of the height-adjustable table.
The purpose of the invention is to provide a control box which enables this and which does not alter the other dimensions of the control box, so that the control box may be mounted within the built-in dimensions provided by the longitudinal members.